1. Field of the Invention:
The present invention relates to the mining of undersea formations, and, more especially, to the recovery of oceanic solids containing metal values from deep submarine deposits, e.g., ocean floors.
2. Description of the Prior Art:
Metal bearing deposits present on the surface of certain ground regions, or strata, covered by seawaters and the oceans constitute potentially enormous sources of metallurgical values. These are in widely differing forms, varying from muds rich in metals to polymetallic nodules and metal-containing chimneys. The abundance of valuable metals in these deposits has heightened interest in the industrial exploitation or mining recovery thereof. However, their recovery presents certain obvious economic and technical problems, as such values are located at ocean depths of up to 6,000 meters. Moreover, the dimensions of these solid particulates vary from a few millimeters to tens of centimeters. This, together with their weight, directly affects the efficiency of any recovery/collection thereof.
It has already been considered, on an experimental scale, to apply the airlift pumping method for the mining of suboceanic deposits/formations (J. P. Jacquemin, J. F. Lapray, R. Porte, "IInd International Colloquium on the Exploitation of the Oceans", Bordeaux, Oct. 1-4, 1974).
According to this technique, air is injected into the lower region of a tube partially submerged in a body of water. The gas lightens the column of water confined in the tube and raises its level. Beginning with a certain stream of air, the two-phase mixture escapes at the upper end of the tube, thereby generating or establishing a pumping effect. However, the raising of heavy or large particles, such as boulders, is very difficult at great depths in view of the low suspension capacity of a two-phase air/water mixture.